Compositions, and Methods and Uses Relating Thereto

ABSTRACT

A fuel oil composition comprising a blended fuel oil having a sulfur content of less than 5000 ppm and an additive wherein the additive is a copolymer comprising maleic anhydride derived units and α-olefin derived units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalApplication No. 63/222,828, filed Jul. 16, 2021 and Great Britain PatentApplication No. 2111108.3, filed Aug. 2, 2021, both of which areincorporated by reference herein in their entireties for all purposes.

FIELD

The present invention relates to fuel oil compositions and to methodsand uses relating thereto. In particular the invention relates to verylow sulfur fuel oil (VLSFO) compositions.

BACKGROUND

The invention relates especially to fuel oils useful in marineapplications. Fuels of this kind are commonly referred to as marinediesel oil (marine fuel oil), marine residue oil (residual fuel oil) orbunker oil (bunker fuel oil). These are typically heavy fuels containinglong chain alkanes and alkenes, high molecular weight cycloalkanes andhighly fused aromatics (asphaltenes). Fuels of this type are often highin sulfur. New regulations (IMO 2020) have recently been introduced bythe International Maritime Organization (IMO) setting a global limit forsulfur in fuel oil on board ships of 0.50 wt % (5000 ppm by weight).This is a significant reduction from the previous limit of 3.5 wt %.

Various approaches have been taken to reduce the sulfur content of thesefuels in order to comply with the new regulations. More catalyticprocessing of fuels is often involved and fuels from multiple sourcesmay be blended to provide a blended fuel with a sulfur content of lessthan 0.50 wt %. However the component fuels mixed into the blends mayhave very different properties.

This has led to fuel stability problems for the new IMO2020 compliantvery low sulfur fuel oils (VLSFO). Typically residual and low sulfurdistillate streams are blended to reach the new sulfur specification,but the component fuel streams that are blended to make the fuel can bevariable quality and often have a level of chemical reactivity. This canlead to oxidative and thermal stability problems over time for theblended fuel, with gums or other insolubles being formed.

Problems due to precipitation of asphaltenes from marine fuels have beenknown for a long time and additives have been developed which helpaddress these issues and reduce asphaltene deposits. These additives areknown as asphaltene dispersants. However for new blended VLSFOcompositions new problems with stability are occurring. It is an aim ofthe present invention to provide a VLSFO having improved oxidativeand/or thermal stability.

SUMMARY

According to a first aspect of the present invention there is provided afuel oil composition comprising a blended fuel oil having a sulfurcontent of less than 5000 ppm and an additive where the additive is acopolymer comprising maleic anhydride derived units and α-olefin derivedunits.

BRIEF DESCRIPTION OF THE DRAWINGS

This patent or application file contains at least one drawing executedin color. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a picture of the centrifuge tube for entries 7 and 1 (fromleft to right) in Table 3 after it has been allowed to stand undisturbedfor 18 hours at ambient temperature.

DETAILED DESCRIPTION

The present invention relates to a fuel oil composition having a sulfurcontent of less than 5000 ppm. Unless otherwise mentioned all referencesto ppm in this specification are to parts per million by weight.

The fuel oil composition of the present invention comprises a blendedfuel oil. Suitably the blended fuel oil comprises at least two componentfuels. The two or more component fuel oils may be selected from residualfuel oils, distillate fuel oils, bio-derived fuel oils, cracked processstreams, synthetic fuels and plastic pyrolysis oils.

Residual fuel oils are the heavy fuel components which remain afterdistillation or refining process. By residual fuel oils we mean toinclude atmospheric tower bottoms and vacuum tower bottoms. Residualfuel oils which have been subjected to hydrotreating or visbreakingprocesses are also regarded as residual fuel oils.

Residual fuel oils have high boiling points and high viscosity, and havehigh sulfur and nitrogen contents.

Unless hydrotreated residual fuel oils comprise high levels of sulfur,for example up 5 wt %, typically 1 to 4 wt %.

Residual fuel oils typically have a nitrogen content of at least 1000ppm and may have a nitrogen content of at least 2000 ppm, for example upto 5000 ppm or up to 10000 ppm.

Atmospheric tower bottoms (ATB) typically have a boiling point of 340°C. or above.

Vacuum tower bottoms (VTB) typically have a boiling point of 550° C. orabove.

Visbreaker residue typically has a boiling range of 340 to 540° C.

The kinematic viscosity of residual fuel oils is typically in the range10 to 15000 mm²/s, preferably 20 to 7500 mm²/s, suitably 50 to 1000mm²/s. Visbreaker residue which is typically derived from VTB typicallyhas a lower viscosity than VTB, often having a viscosity around a fifthof that of the VTB from which it is derived.

Kinematic viscosity may be measured according to ISO 3104 at 50° C.

The pour point of residual fuel oils may be from −10 to 85° C.,preferably from −5 to 60° C., for example from 0 to 45° C.

Pour point may be measured according to ISO 3016.

The asphaltene content of the residual fuel oil is preferably less than5 wt %, more preferably less than 2 wt %, suitably less than 1 wt %.

Suitable methods for measuring asphaltene content include IP-469 (SARAanalysis).

By distillate fuels we mean to include straight run distillate fuels,hydrotreated distillate fuels (for example low sulfur diesel fuel orvery low sulfur diesel fuel), kerosene, light gas oil, heavy gas oil andvacuum gas oil.

Distillate fuels may have a boiling point within the range 180 to 550°C.

Straight run distillate fuels are obtained directly from thedistillation column and used without any further treatment.

Middle distillate fuel oil/diesel fuel oil suitably has a boiling rangeof 200 to 350° C.,

Kerosene typically has a boiling range of 193 to 271° C.

Light gas oil typically has a boiling range of 271 to 321° C.

Heavy gas oil typically has a boiling range of 321 to 425° C.

Light vacuum gas oil typically has a boiling range of 425 to 510° C.

Heavy vacuum gas oil typically has a boiling range of 510 to 564° C.

Straight run middle distillate fuels typically have a sulfur content of0.5 to 2 wt %. However distillate fuels are commonly hydrotreated in aprocess which reduces the sulfur content.

Low sulfur diesel fuels have a sulfur content of less than 500 ppm. Insome countries they may have a sulfur content of less than 200 ppm.

Ultra low sulfur diesel fuels have a sulfur content of less than 50 ppm.In some countries they may have a sulfur content of less than 15 ppm orless than 10 ppm.

By cracked process streams we mean to refer to fuels obtained fromcatalytic cracking of fuel oils. Such fuel components typically containreactive groups such as olefins. By cracked process streams we mean toinclude cracked light gas oil, cracked heavy gas oil, light cycle oil,heavy cycle oil and fluid catalytic cracker slurry oil.

Light cycle oil typically refers to the fluid catalytic cracker (FCC)product distilling in the range of 200 to 350° C.

Heavy cycle oil typically refers to the FCC product distilling in therange 350 to 500° C.

Slurry oil is a mixture comprising the FCC residue and catalyst fines(typically silica and/or alumina).

Suitable bio-derived fuel oils include biodiesel fuels and secondgeneration biodiesel fuels. Biodiesel as defined by ASTM specificationD-6751 (the entire teachings of which are incorporated herein byreference) and EN 14214 are fatty acid mono alkyl esters of vegetable oranimal oils. Suitable biofuel may be made from any fat or oil source,including tallow, but is preferably derived from a vegetable oil, forexample rapeseed oil, palm oil, palm kernel oil, coconut oil, corn ormaize oil, sunflower oil, safflower oil, canola oil, peanut oil,cottonseed oil, jatropha oil (physic nut), used cooking oil or soybeanoil. Preferably it is a fatty acid alkyl ester (FAAE). More specificallythe biofuel may comprise rapeseed methyl ester (RME) and/or soybeanmethyl ester (SME) and/or palm oil methyl ester (PME) and/or jatrophaoil methyl ester.

A biofuel may suitably be second generation biodiesel. Second generationbiodiesel is derived from hydrotreatment of renewable resources such asvegetable oils and animal fats. Second generation biodiesel may besimilar in properties and quality to petroleum based fuel oil streams.

Biofuels typically have very low sulfur contents, suitably less than 100ppm. They have similar boiling points to mineral distillate fuels.

By synthetic fuel oils we mean to include any synthetically preparedhydrocarbon fuel oils, for example those obtained by Fischer Tropschprocesses. Suitable fuels of this type include heavier Fisher-Tropschfuels for example as described in U.S. Ser. No. 10/294,431.

Plastic pyrolysis oils are obtained from plastic waste via athermochemical process based on pyrolysis and hydrotreatment. Plasticpyrolysis oils typically have a boiling range of 170 to 370° C. and alow sulfur content, for example less than 100 ppm or less than 50 ppm.

The fuel oil composition of the present invention comprises a blendedfuel oil. This is suitably obtained by blending two or more componentfuels.

Preferably the blended fuel oil comprises at least one residual fuelcomponent and at least one further non-residual fuel component.

Preferably the blended fuel oil comprises at least 1 wt % residual fuelcomponents.

The blended fuel oil may comprise at least 5 wt % residual fuelcomponents.

The blended fuel oil preferably comprises from 1 to 50 wt % residualfuel components.

The blended fuel oil may comprise two or more residual fuel components.

Preferably the blended fuel oil comprises at least one residual fuelcomponent and at least one further fuel component.

In some embodiments the blended fuel oil comprises from 5 to 95 wt %residual fuel components and from 95 to 5 wt % one or more further fuelcomponents selected from distillate fuel components and/or cracked fuelcomponents.

In some embodiments the blended fuel oil comprises 5 to 75 wt %,preferably 10 to 50 wt % straight run distillate fuel.

In some embodiments the blended fuel oil comprises 5 to 75 wt %,preferably 10 to 50 wt % cracked process streams.

In some embodiments the blended fuel oil comprises 5 to 75 wt %,preferably 10 to 50 wt % light cycle oil.

The properties of a blended fuel depend on the properties of thecomponent fuels from which they are made and the proportions of eachfuel in the blend.

The stability of a blended fuel depends on the nature and relativeamounts of the component fuels present in the blended fuels.

Residual and cracked components generally lead to reduced stability.

The inclusion of treated distillates for example hydrotreateddistillates and synthetic fuels tends to improve the stability of theblended fuel.

The blended fuel oil has a sulfur content of less than 5000 ppm. It mayhave a sulfur content of less than 4000 ppm, for example less than 3000ppm, less than 2000 ppm or less than 1000 ppm.

Preferably the blended fuel oil has a pour point as measured accordingto ISO 3016 of from −10 to 40° C., preferably from −10 to 25° C., morepreferably from −10 to 10° C.

Preferably the blended fuel oil has a kinematic viscosity as measured byISO 3104 at 40° C. of less than 200 mm²/s, preferably less than 100mm²/s, suitably between 1 and 20 mm²/s, preferably from 1.4 to 10 mm²/s.

The blended fuel oil may have a kinematic viscosity of from 0.1 to 200mm²/s, for example 1 to 100 mm²/s, for example 1.4 to 15 mm²/s asdetermined by ISO 3014 at 40° C.

Suitably the blended fuel oil has an asphaltene content of less than 6wt %, for example less than 2 wt %, such as less than 0.5 wt %.

The fuel oil compositions of the present invention comprise an additivewhich is a copolymer comprising maleic anhydride derived units andα-olefin derived units.

The copolymer is suitably an alternating copolymer and is prepared byreacting maleic anhydride with an α-olefin. Means for carrying out suchreactions will be well known to those skilled in the art and aredescribed, for example in U.S. Pat. Nos. 4,240,916, 3,560,456 and4,151,069.

The copolymer additive of the invention is suitably prepared by reactingmaleic anhydride with an α-olefin in a molar ratio of from 3:1 to 1:3,preferably 2:1 to 1:2, more preferably from 1.5:1 to 1:1.5, for exampleabout 1:1.

Preferably the α-olefin has from 6 to 40 carbon atoms, preferably from10 to 36 carbon atoms, preferably from 12 to 36 carbon atoms, forexample from 16 to 32 carbon atoms. Most preferably the α-olefin hasfrom 18 to 30 carbon atoms, for example from 20 to 28 carbon atoms.

To form the copolymer additive of the invention a mixture of α-olefinsmay be used.

In one preferred embodiment a mixture of α-olefins having 20 to 24carbon atoms is used.

In one embodiment a mixture of α-olefins having 24 to 28 carbon atoms isused, for example a mixture having 26 to 28 carbon atoms.

The present invention relates to a copolymer comprising maleic anhydridederived units and α-olefin derived units.

The copolymer directly obtained from the reaction of an α-olefin andmaleic anhydride comprises alkyl chains and anhydride functional groups.

In some embodiments the anhydride groups may be further reacted. Forexample in some embodiments the anhydride groups may be hydrolysed toprovide carboxylic acid functional groups.

In some embodiments the anhydride and/or hydrolysed acid product may bepartially or fully further functionalised, for example by reaction withamines and/or alcohols to incorporate ester and/or amide and/or imidefunctional groups into the copolymer.

In preferred embodiments the copolymer is not further functionalised inthis way and the maleic anhydride derived units are present asunderivatized anhydride moieties and/or as carboxylic acid moieties.

Most preferably the maleic anhydride derived units of the copolymercontain anhydride groups. Suitably the additive comprises a copolymerobtained directly from the reaction of an α-olefin with maleicanhydride.

Preferred copolymers for use herein have a number average molecularweight of from 1000 to 50000, preferably from 2000 to 40000, suitablyfrom 2500 to 30000, for example from 3000 to 25000.

Preferably the copolymer has a number average molecular weight of from5000 to 20000, in one embodiment the copolymer has a number averagemolecular weight of from 5000 to 10000. In one embodiment the copolymerhas a number average molecular weight of from 8000 to 15000.

The copolymer additive is preferably present in the fuel oil compositionin an amount of at least 10 ppm, preferably at least 30 ppm.

Preferably the copolymer additive is present in the fuel oil compositionin an amount of from 20 to 10000 ppm, preferably 50 to 5000 ppm,suitably from 60 to 3000 ppm, more preferably from 100 to 1000 ppm.

In some embodiments the fuel oil composition of the present inventioncomprises a single component fuel. The fuel oil composition of thepresent invention preferably comprises a blended fuel oil formed fromtwo or more component fuels. The copolymer additive of the invention maybe added to the blended fuel or it may be added to a component fuelbefore it is mixed with further components.

When formulating a blended fuel oil it is typical that one or morecomponent fuels used to prepare the blended fuel will be less stablethan other component fuels. For example some component fuels may be moresusceptible to thermal and/or oxidative degradation. Thus it may beadvantageous to add the copolymer additive to a particular componentfuel prior to admixture with other component fuels.

In some cases SARA analysis may be carried out on one or more componentfuels or the blended fuel.

SARA analysis (percent saturates, aromatics, resins and asphaltenes) canbe performed to obtain information about the compositional nature of theblended fuel. SARA analysis is used to determine the properties of anoil that contribute to instability and its potential for fouling whenprocessed or blended with other oils. Asphaltenes and saturated,straight-chained hydrocarbons (n-paraffins) can become unstable andprecipitate out of an oil as a function of composition, temperature,pressure and/or time. Aromatics and resins on the other hand tend tohelp stabilize a fuel oil sample.

According to a second aspect of the invention there is provided a methodof preparing a fuel oil composition, the method comprising admixing anadditive with a first component fuel and with a second component fuelwherein the resultant fuel oil composition has a sulfur content of lessthan 5000 ppm and wherein the additive is a copolymer comprising maleicanhydride derived units and α-olefin derived units.

Preferred features of the second aspect are as defined in relation tothe first aspect.

Preferably the copolymer additive is mixed with the first component fuelbefore the first component fuel is mixed with the second component fuel.

The copolymer additive improves the stability of the fuel oilcompositions of the invention. Thus the fuel oil composition of theinvention has improved stability compared with an equivalent unadditisedfuel oil.

According to a third aspect of the invention there is provided a methodof improving the stability of a blended fuel oil having a sulfur contentof less than 5000 ppm, the method comprising mixing into the fuel oil anadditive which is a copolymer comprising maleic anhydride derived unitsand α-olefin derived units.

In some embodiments the additive is mixed into a component fuel used toprepare the fuel oil composition.

According to a fourth aspect of the invention there is provided a use ofa copolymer comprising maleic anhydride derived units and α-olefinderived units as an additive to improve the stability of a blended fueloil having a sulfur content of less than 5000 ppm.

Preferred features of the third and fourth aspects of the invention areas defined in relation to the first aspect.

Further preferred features of the invention will now be described.

The present invention involves the use of an additive to improve thestability of a fuel oil having a sulfur content of less than 5000 ppm.

By improving the stability of the fuel oil we mean to include any meansby which the additised fuel may be considered to be more stable than anequivalent unadditised fuel.

An improvement in stability may result from reduced degradation due toheat, light or oxidation.

An improvement in stability may provide a reduction in the formation ofgums, sediments or other insolubles.

An improvement in stability may reduce or inhibit precipitation.

An improvement in stability may provide improved dispersion ofinsolubles in a fuel.

An improvement in stability may improve filterability and/or reducefilter blocking.

An improvement in stability may involve colour stability and/or reduceddiscolouration.

The present invention may provide improved storage stability. Improvedstorage stability may be measured by a reduction in sediment formationand/or reduced precipitation and/or improved filterability and/orimproved colour stability.

The present invention may provide improved thermal stability. This maybe measured by a reduction in the formation of thermal degradationproducts such as gums and sediments and/or reduced discolouration.

The present invention may provide improved oxidation stability. This maybe measured by a reduction in the formation of oxidative degradationproducts such as gums and sediments and/or reduced discolouration.

A particular advantage of the present invention is the reduction in thelevels of gums and insolubles which are not reduced by traditionalasphaltene dispersants used in marine fuel oils. These additives areknown to the person skilled in the art and include, for examplealkylphenol resins, sulfonated alkyl, alkyl compounds and polyesterpolyamides/imides. Such compounds are described in WO2009/013536, U.S.Pat. No. 9,034,093 and US2017/0198174.

Improvement in fuel stability can be measured by any suitable means.Methods by which stability of fuels can be measured are well known tothose skilled in the art.

One especially useful means by which the effect of the present inventioncan be measured is by determining total sedimentation using the methodsdescribed in ISO10307-1 and ISO10307-2. Alternatively, the effect of thepresent invention can be measured by determining total sedimentationusing the methods described in ASTM D4870.

Other methods for measuring improved fuel stability include ASTN D4740Spot Test, ASTM D7061 Turbiscan Method, ATSM D7112 PORLA Method and ASTMD7157 Rofa Method (S-value).

Further suitable methods for measuring improved fuel stability includeASTM D97 (modified)—Manual Pour Point; ASTM D4530— Micro-Carbon ResidueTest; ASTM D5949— Automated Pour Point Testing; ASTM D7169— ParaffinContent & Distribution Analysis; IP 469— SARA Compositional Analysis;and Digital Imaging (via Cross Polar Microscopy) & Particle SizeEvaluations.

The fuel oil compositions of the invention may further comprise one ormore further additives. Any additives commonly incorporated into fuelsfor marine applications may be included. The formation of suitable fuelcompositions and additive packages for fuels will be within thecompetence of the person skilled in the art.

Additive classes which may be included in the fuel oil compositions ofthe present invention include:

-   -   (i) conductivity improvers;    -   (ii) combustion improvers;    -   (iii) asphaltene dispersants;    -   (iv) fuel antioxidants;    -   (v) cold flow improvers;    -   (vi) wax anti-setting agents;    -   (vii) biofuel instability inhibitors;    -   (viii) blended fuel separation inhibitors;    -   (ix) other detergents/dispersants.

Suitable conductivity improver additives (i) for use herein include:alpha-olefin-sulfone copolymer class—polysulphone and quaternaryammonium salt (for example as described in U.S. Pat. No. 3,811,848);polysulphone and quaternary ammonium salt amine/epichlorhydrin adductdinonylnaphthylsulphonic acid (for example as described in U.S. Pat. No.3,917,466); copolymer of an alkyl vinyl monomer and a cationic vinylmonomer (for example as described in U.S. Pat. No. 5,672,183);alpha-olefin-maleic anhydride copolymer class (for example as describedin U.S. Pat. No. 4,416,668); alpha-olefin-acrylonitrile copolymers (forexample as described in U.S. Pat. No. 4,388,452);alpha-olefin-acrylonitrile copolymers and polymeric polyamines (forexample as described in U.S. Pat. No. 4,259,087); copolymer of analkylvinyl monomer and a cationic vinyl monomer and polysulfone (forexample as described in U.S. Pat. No. 6,391,070); and acrylic-typeester-acrylonitrile copolymer and polymeric polyamine (for example asdescribed in U.S. Pat. Nos. 4,537,601 and 4,491,651).

In some preferred embodiments the conductivity improver comprises apolysulfone component.

In some preferred embodiments the conductivity improver comprises apolymeric nitrogen-containing conductivity improver.

In some preferred embodiments the conductivity improver comprises apolyamine compound.

In some preferred embodiments the conductivity improver is a compositioncomprising both a polyamine component and a polysulfone component,optionally in combination with a quaternary ammonium salt, for exampleas described in U.S. Pat. No. 3,917,466.

Preferred conductivity improvers for use in the fuel oil compositions ofthe invention are described in WO2009/013536.

Suitable combustion improvers (ii) include metal compounds, organiccompounds and mixtures thereof.

Suitable combustion improvers are described in WO2009/013536.

Some preferred combustion improvers containing a metal compound and anorganic compound are described in EP1899440.

The metal compound is preferably selected from an iron compound, amanganese compound, a calcium compound, a cerium compound, and mixturesthereof.

The organic compound is preferably selected from a bicyclic monoterpene,substituted bicyclic monoterpene and mixtures thereof.

Preferably the organic compound is camphor.

Preferred metal compounds are ferrocene and substituted ferrocenes.

Other suitable combustion improvers are cetane improvers such as alkylnitrates or dialkyl peroxides, for example as described inUS20190127657.

An especially preferred cetane improver is 2-ethylhexyl nitrate.

Suitable asphaltene dispersants (iii) for use in the fuel oilcompositions of the present invention include alkoxylated fatty aminesor derivatives thereof; alkoxylated polyamines; alkane sulphonic acids;aryl sulphonic acids; sarcosinates; ether carboxylic acids; phosphoricacid esters; carboxylic acids and derivatives thereof;alkylphenol-aldehyde resins; hydrophilic-lipophilic vinylic polymers;alkyl substituted phenol polyethylene polyamine formaldehyde resins;alkyl aryl compounds; alkoxylated amines and alcohols; imines; amides;zwitterionic compounds; fatty acid esters; lecithin and derivativesthereof; and derivatives of succinic anhydride and succinamide.

Suitable asphaltene dispersants are described in WO2009/013536.

A particularly preferred class of asphaltene dispersants for use hereinare alkyl phenol aldehyde resins, for example those described inparagraphs [0017] to [0038] of US2007221539. Compounds derived from C3to C12 alkyl or alkenyl phenols, especially nonylphenol are particularlypreferred.

Combinations of alkyl phenol aldehyde resins and poly(meth)acrylates asdescribed in U.S. Pat. No. 5,021,498 are useful as asphaltenedispersants.

Further suitable asphaltene dispersants include alkoxylated fattypolyamines for example as described in U.S. Pat. Nos. 6,488,724 and5,421,993. Also useful are alkoxylated derivatives of simple polyamines,for example a block copolymer derived from ethylene diamine, ethyleneoxide and propylene oxide. An example of such a compound is availablefrom Clariant under the trade mark GENAPOL®.

Suitable fuel antioxidants (iv) suitable for use in the presentinvention include phenolic antioxidants, sulphurized phenolicantioxidants and aromatic amine antioxidants.

Suitable antioxidants are described, for example, in WO2009/013536, U.S.Pat. Nos. 3,556,748 and 5,509,944.

Preferred antioxidants for use herein are aromatic amines, for examplephenylene diamine.

Cold flow improvers (v) suitable for use in the present inventioninclude copolymers of alkenes and unsaturated esters, alkylmethacrylatepolymers, polyoxyalkylene esters, ethers, ester/ethers and mixturesthereof.

Suitable cold flow improvers for use herein are described inWO2009/013536 and US2017/0233670.

Particular preferred cold flow improvers are ethylene vinyl acetatecopolymers and terpolymers. These are described for example inparagraphs [0026] to [0032] of US20170233670.

Typical copolymers are those of ethylene and vinyl esters such as vinylacetate. Propene may also be included.

Terpolymers may further comprise vinyl neodecanotate, vinyl2-ethylhexanoate, methyl acylate or 2-ethylhexyl acrylate.

Another preferred class of cold flow improvers are comb polymers. Theseare known to the person skilled in the art and include:

-   -   polyalkyl(meth) acrylates or copolymers thereof;    -   maleic anhydride-α-olefin copolymers which are subsequently        reacted with alcohols (eg. C10 to C28 alcohols) to form esters        or subsequently reacted with primary fatty amines;    -   fumarate vinyl ester copolymers, for example fumarate vinyl        acetate; and    -   poly(α-olefin)homo or copolymers.

Some suitable comb polymers are described in paragraphs [0067] to [0070]of US20170233670.

Wax anti-settling agents (vi) useful as stabilisers in the presentinvention include certain polyimide and maleic anhydride olefincopolymers.

Suitable additives of this type for use herein are described inWO2009/013536.

Other suitable wax settling additives include: those described in U.S.Pat. No. 4,402,708 such as the reaction product of phthalic anhydrideand ditallow fatty amide; combinations of such additives and ethylenevinyl acetate copolymers, for example as described in U.S. Pat. No.4,481,013; the fatty amide derivatives described in U.S. Pat. No.5,071,445; and the copolymers described in U.S. Pat. No. 5,391,632,including in particular the compound of comparative example 25.

Further compounds which may be useful as wax anti-settling agents and/oras cold flow inhibitors are described in EP 743972 and EP 743974.

Biofuel instability inhibitors (vii) function mainly to dispersepolymers or high molecular weight compounds either found in the biofuelsas the bi-product of oxidation or thermal breakdown. Biofuel instabilityinhibitors useful herein include polymers of: ethylene and unsaturatedesters; vinyl alcohols, vinyl ethers and their ester with organic acids;propylene, ethylene, isobutylene adducts with unsaturated carboxylicacids (such as maleic and fumaric acids) and their amide or imidederivatives; acrylic acids and their amide or esters derivatives;polystyrenes; and polymers made from combinations of these monomers.

A blended fuel separation inhibitor (viii) acts to maintain two or morefuels in a dispersed or blended form. Loss of uniformity and mobility offuel may also occur when there is phase separation within such a fuel.Fuel blends may commonly be made in-tank when ships dock and may sourcewhatever fuel is available at the locality at a favourable price. Lackof stability may occur, for example, when two or more differentdistilled fuels are blended, or when a biofuel is blended with adistilled fuel.

Many compounds as blended fuel separation inhibitors include compoundsdescribed above and selection of suitable additives will be within thecompetence of the person skilled in the art.

Detergent/dispersant compounds (ix) suitable for use herein include anycommonly known nitrogen-containing or non-nitrogen containing detergentcompounds. Such compounds typically include a long chain hydrophobictail and a polar head group. Suitable hydrophobic groups arepolyisobutene groups and polar head groups may contain nitrogen and/oroxygen containing functional groups such as amides, amines,succinimides, acids and esters.

Preferred acylated nitrogen-containing dispersants are the reactionproduct of a carboxylic acid derived acylating agent and an amineincluding at least one primary or secondary amine group.

A preferred acylated nitrogen-containing compound for use herein isprepared by reacting a poly(isobutene)-substituted succinic acid-derivedacylating agent (e.g., anhydride, acid, ester, etc.) wherein thepoly(isobutene) substituent has a number average molecular weight (Mn)of between 170 to 2800 with a mixture of ethylene polyamines having 2 toabout 9 amino nitrogen atoms, preferably about 2 to about 8 nitrogenatoms, per ethylene polyamine and about 1 to about 8 ethylene groups.

Especially preferred polyisobutenyl succinimide additives include thoseobtained from the condensation reaction of a polyisobutenyl succinicanhydride derived from polyisobutene of Mn approximately 750 orapproximately 1000 with a polyethylene polyamine mixture of averagecomposition approximating to tetraethylene pentamine.

Preferred further additives for inclusion in the fuel oil compositionsof the invention include acylated nitrogen-containing dispersants,alkylphenol-aldehyde resins and phenylene diamine antioxidants.

In a preferred embodiment the phenolic resin is a substituted phenolicresin. More preferably the phenolic resin is the reaction product ofsubstituted phenol and an aldehyde.

More preferably the phenolic resin is the reaction product ofsubstituted phenol and an aldehyde having 1-22, preferably 1-7 carbonatoms, for example formaldehyde.

Preferably the phenolic resin is a C₉-C₂₄ phenolic resin.

More preferably the phenolic resin is the reaction product of a C₉-C₂₄phenol and formaldehyde, or of t-butyl phenol and an aldehyde having1-22, preferably 1-7, carbon atoms, for example formaldehyde.

Preferred additives for improving the low temperature properties of thefuel oil compositions are described in US2017/0233670.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatized maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatized maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents, wherein the copolymer has a number average molecular weightof from 5000 to 10000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatized maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents, wherein the copolymer has a number average molecular weightof from 8000 to 15000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components, whereinthe copolymer has a number average molecular weight of from 5000 to10000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 20 to 24 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components, whereinthe copolymer has a number average molecular weight of from 8000 to15000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents, wherein the copolymer has a number average molecular weightof from 5000 to 10000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % straight run distillate fuelcomponents, wherein the copolymer has a number average molecular weightof from 8000 to 15000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components, whereinthe copolymer has a number average molecular weight of from 5000 to10000.

In some preferred embodiments the first, second, third or fourth aspectsof the invention may relate the use of a copolymer comprisingunderivatised maleic anhydride derived units and units derived from amixture of α-olefins having 26 to 28 carbons in combination with ablended fuel oil comprising at least 1 wt % residual fuel components and5 to 75 wt %, preferably 10 to 50 wt % cracked fuel components, whereinthe copolymer has a number average molecular weight of from 8000 to15000.

The present invention will now be further described with reference tothe following non-limiting examples.

Example 1

Additives A to D (inventive) were prepared by the reaction of equimolaramounts of α-olefin and maleic anhydride in the presence of radicalinitiator and solvent for 5 hours. The reaction conditions aresummarized in Table 1. After completion of the reaction, the reactionsolvents were removed under reduced pressure to provide the polymericproducts, which were then diluted to a polymer concentration of 40 wt %using Aromatic 150 solvent.

GPC analysis of the molecular weight (MW) distribution is also shown inTable 1

Gel permeation chromatography (GPC) was carried out using a WatersStyragel® HR column, eluting with tetrahydrofuran (1 mL/min) at 39° C.Detection was by refractive index and the product molecular weightdistribution (Mn, Mw and polydispersity) was calculated relative topolystyrene standards.

TABLE 1 Radical Reaction Reaction Polymer MW by GPC Additive α-olefininitiator solvent temp (° C.) Mn Mw PD A C20-24 di(tert- Diisobutyl 1602292 4600 2.0 butyl)peroxide ketone B C26-28 di(tert- Diisobutyl 1604190 6424 1.53 butyl)peroxide ketone C C20-24 Trigonox 21S* toluene 809769 22155 2.27 D C26-28 Trigonox 21S* toluene 80 12910 28832 2.23*tert-Butyl peroxy-2-ethylhexanoate, commercially available from Nouryon

Example 2

Additives A to D as shown in Table 1 were added to a marine fuelcomplying with IMO 2020 standards. The marine fuel comprised a blend ofdistillate and residual fuel components, having a TSE values of 0.09%(m/m) as measured by ISO10307-1.

Comparative fuel compositions were prepared by dosing the knownasphaltene dispersants E, F, G, H and I into the same fuel.

Compositional information for the additives used in the comparativeexamples is shown in Table 2.

TABLE 2 Additive Description E Marine fuel additive package containingan alkylphenol resin, an alkoxylated polyamine and an acylatednitrogen-containing stabilizer/dispersant F Acylated nitrogen-containingstabilizer/dispersant G Phenolic resin prepared from dodecyl phenol,tert-octyl phenol and formaldehyde H Phenolic resin prepared fromtetradecylphenol and formaldehyde

The fuel compositions were then subjected to a heptane dispersant testcarried out in the following manner:

The additised or unadditised fuel oil (0.1 g) was added to heptane (6.77g, 9.9 mL) in a graduated centrifuge tube. After mixing thoroughly, thecentrifuge tube was allowed to stand undisturbed for 18 hours at ambienttemperature. The sample was then visually evaluated and given a ratingof good, moderate or poor for dispersancy.

A sample was also run in the absence of additive. The results of theheptane dispersant tests are shown in Table 3.

TABLE 3 Treat Rate (ppm Visual inspection Entry Additive Type by weightActive) rating 18 hours 1 A inventive 1500 Good 2 B inventive 1500 Good3 E comparative 1500 Moderate 4 F comparative 1500 Poor 5 G comparative1500 Poor 5 H comparative 1500 Poor 7 none comparative — Poor* *For theunadditised test, visual inspection took place after 1 hour

The additives of the invention showed superior dispersancy of the gumsand sediments that were present within the IMO 2020 compliant marinefuel, when compared to the comparative examples. FIG. 1 shows thecentrifuge tube for entries 7 and 1 (from left to right) in Table 3after it has been allowed to stand undisturbed for 18 hours at ambienttemperature.

Example 3

The effect of an additive of the invention on TSP (total sedimentpotential) was evaluated in a different VLSFO, which comprised a blendof distillate and residual fuel components.

Prior to testing with additives, the TSE (existent sediment withoutthermal aging) for the fuel was measured as 0.13% (m/m). The SARAanalysis (IP-469) provided saturates 49.8 wt %, aromatics 36.50 wt %,resins 8.80 wt % and asphaltenes 4.90 wt %]

Total sediment existent (TSE) was measured according to ISO 10307-1. Theresults are expressed as the mass percentage of total sediment, to thenearest 0.01% (m/m).

Total sediment potential (TSP) was measured by thermally aging the testsample for 24 hours at 100° C. according to ISO 10307-2 (Procedure A)followed by hot filtration according to ISO 10307-1. The results areexpressed as the mass percentage of total sediment, to the nearest 0.01%(m/m).

Compositional information for the additives used in the comparativeexamples is shown in Table 4.

TABLE 4 Additive Compositional Information J Amine based stabilityadditive K Phenolic resin, high molecular weight

The TSP was then measured and the results are shown in Table 5.

TABLE 5 TSP measurements Treat Rate (ppm TSP Entry Additive Type byweight active) (% m/m) 1 none comparative — 0.42 2 B inventive 1500 0.143 J comparative 1500 0.30 4 K comparative 1500 0.22

The results showed that the test fuel was unstable. For the unadditisedfuel the TSP result (0.42% m/m) was significantly higher than the TSE(0.13% m/m). Unexpectedly, inventive additive B was highly effective instabilizing the test fuel (Table 5, entry 2). For the fuel additisedwith additive B the measured TSP was essentially unchanged compared tothe TSE of the unadditised fuel.

1. A fuel oil composition comprising a blended fuel oil having a sulfurcontent of less than 5000 ppm and an additive wherein the additive is acopolymer comprising maleic anhydride derived units and α-olefin derivedunits.
 2. The fuel oil composition according to claim 1 wherein the fueloil comprises at least one distillate fuel component and at least oneresidual fuel component.
 3. The fuel oil composition according to claim2 wherein the fuel oil comprises from 5 to 95 wt % of residual fuelcomponents and from 5 to 95 wt % of one or more fuel components selectedfrom distillate fuel components and cracked fuel components.
 4. The fueloil composition according to claim 1 wherein the maleic anhydridederived units of the copolymer are present as underivatized anhydridemoieties and/or as carboxylic acid moieties.
 5. The fuel oil compositionaccording to claim 1 wherein the α-olefin derived units contain 12 to 36carbon atoms.
 6. The fuel oil composition according to claim 1 whereinthe maleic anhydride/α-olefin copolymer is present in an amount of from50 to 5000 ppm.
 7. The fuel oil composition according to claim 1 whereinthe copolymer additive has a number average molecular weight of 5000 to20000.
 8. The fuel oil composition according to claim 1 which comprisesone or more further additives selected from: (i) conductivity improvers;(ii) combustion improvers; (iii) asphaltene dispersants; (iv) fuelantioxidants; (v) cold flow improvers; (vi) wax anti-setting agents;(vii) biofuel instability inhibitors; (viii) blended fuel separationinhibitors; (ix) other detergents/dispersants.
 9. The fuel oilcomposition according to claim 1 wherein the fuel oil comprising theadditive has improved stability compared with an equivalent unadditisedfuel oil.
 10. A method of preparing a fuel oil composition, the methodcomprising admixing an additive with a first component fuel and with asecond component fuel wherein the resultant fuel oil composition has asulfur content of less than 5000 ppm and wherein the additive is acopolymer comprising maleic anhydride derived units and α-olefin derivedunits.
 11. The method according to claim 10 wherein the additive ismixed with the first component fuel before the first component fuel ismixed with the second component fuel.
 12. The method according to claim10 wherein one or more further component fuels are mixed to provide thefuel oil composition.
 13. A method of improving the stability of ablended fuel oil having a sulfur content of less than 5000 ppm, themethod comprising mixing into the fuel oil an additive which is acopolymer comprising maleic anhydride derived units and α-olefin derivedunits.
 14. The method according to claim 13 wherein the additive ismixed into a component fuel used to prepare the fuel oil composition.15. (canceled)
 16. The method according to claim 13 wherein theimprovement in stability is measured by improved storage stabilityand/or improved thermal stability and/or improved oxidation stability.